Multiple-input and multiple-output (MIMO) is a technique for using multiple transmit and receive antennas to multiply the capacity of a radio link and exploit multipath propagation. Full dimension MIMO (FD-MIMO) involves multiple transmit and receive antennas that can form beams in both horizontal and vertical directions such that the beams can cover anywhere in three-dimensional space in the vicinity of the multiple antennas.
Spatial multiplexing is a transmission technique in MIMO wireless communication. In spatial multiplexing, a datastream is divided into different substreams and transmitted in parallel to a destination device. Each substream is separately encoded and transmitted via a different one of multiple transmit antennas. At the destination wireless device, antennas, corresponding in number to the number of transmit antennas, receive the encoded substreams and associated receiver circuitry decodes each substream. The circuitry then recombines the substreams into the original datastream. Each separately encoded substream, transmitted by a different MIMO transmit antenna, is referred to as a “spatial layer.” Spatial multiplexing in MIMO communication increases the effective data transmission throughput to a destination wireless device.